Effect of different soil conditions on magnetic parameters of power-plant fly ashes

The effect of soil conditions on magnetic parameters of anthropogenic ferrimagnetics was studied. Fly ash from a coal burning power plant (Pocerady, Czech Republic) was used as original contaminant material. whereas soil-reactive medium was modelled by different soil solutions. Magnetic susceptibility, hysteresis parameters, and thermomagnetic curves were measured for samples that under-went different leaching time periods. Virtually constant magnetic susceptibility values were obtained independently on the soil medium (acid and neutral). On the other hand, the original highly nonstoichiometric maghemite phase has been rapidly transformed to stable magnetite. In some cases (model of free-draining soils), further decrease of Curie temperature (T-C) to 550-560 degreesC is observed. Unstable maghemite phase was not identified in contaminated soil horizons in the surroundings of the power plant. (C) 2001 Elsevier Science B.V. All rights reserved.